title: NuMA localization, stability, and function in spindle orientation involve 4.1 and Cdk1 interactions.
abstract: The epidermis is a multilayered epithelium that requires asymmetric divisions for stratification. A conserved cortical protein complex, including LGN, nuclear mitotic apparatus (NuMA), and dynein/dynactin, plays a key role in establishing proper spindle orientation during asymmetric divisions. The requirements for the cortical recruitment of these proteins, however, remain unclear. In this work, we show that NuMA is required to recruit dynactin to the cell cortex of keratinocytes. NuMA's cortical recruitment requires LGN; however, LGN interactions are not sufficient for this localization. Using fluorescence recovery after photobleaching, we find that the 4.1-binding domain of NuMA is important for stabilizing its interaction with the cell cortex. This is functionally important, as loss of 4.1/NuMA interaction results in spindle orientation defects, using two distinct assays. Furthermore, we observe an increase in cortical NuMA localization as cells enter anaphase. Inhibition of Cdk1 or mutation of a single residue in NuMA mimics this effect. NuMA's anaphase localization is independent of LGN and 4.1 interactions, revealing two distinct mechanisms responsible for NuMA cortical recruitment at different stages of mitosis. This work highlights the complexity of NuMA localization and reveals the importance of NuMA cortical stability for productive force generation during spindle orientation.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham, NC 27710 Department of Dermatology, Duke University Medical Center, Durham, NC 27710.
authors.forename: Lindsey
authors.initials: L
authors.lastname: Seldin
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Poulson
authors.forename: Henry P
authors.initials: HP
authors.lastname: Foote
authors.forename: Terry
authors.initials: T
authors.lastname: Lechler
mesh_terms: D000705:Anaphase; D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D000072159:Dynactin Complex; D004398:Dyneins / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D008941:Spindle Apparatus / Q000378:metabolism*; D013314:Stress, Mechanical; D013329:Structure-Activity Relationship
chemical_list: D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D000072159:Dynactin Complex; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; C489080:Numa1 protein, mouse; C028841:erythrocyte membrane band 4.1 protein; D016203:CDC2 Protein Kinase; D004398:Dyneins